PROJECT SUMMARY/ABSTRACT Determining the mechanisms by which the human brain generates cognition, perception, and emotion hinges upon quantifying the relationships between coordinated brain activity and behavior. NIH-funded brain mapping initiatives such as the Human Connectome Project (HCP) and the Adolescent Cognitive and Behavioral Development (ABCD) study, have accelerated the production of large brain connectivity (i.e. connectome) and behavioral datasets. Contemporary connectome research views the brain as a large-scale, complex network composed of nonadjacent, yet connected brain regions. We propose to leverage the inherent network architecture of the connectome in order to probe fundamental biological mechanisms underlying the development of executive function and internalizing symptoms. In pursuit of this research question, this application proposes to formalize and validate in house analysis pipelines into a Network Level Analysis (NLA) toolbox as a comprehensive, versatile tool for use in connectome-wide association studies. The proposed NLA toolbox fulfills BRAIN Initiative goal #5 to ?Produce conceptual foundations for understanding the biological basis of mental processes through development of new theoretical and data analysis tools?. While the research focus of this career transition award is on the application of NLA to developmental mechanisms of executive function and emotion regulation, this versatile analytic tool will be transformative to connectome data analysis across species, across the lifespan, and in health and disease. As part of tool development, the applicant will validate multiple NLA approaches using in silico connectome-behavior relationships and establish sensitivity and specificity of network level findings as compared to the connectome-wide control of familywise error rate (K99 Aim 1). The applicant will then establish test-retest reliability of NLA approaches using in vivo human connectome and behavioral data available from the HCP-Young Adult cohort (N=1105), and establish brain networks underlying healthy adult executive and emotional function (K99 Aim 2). During the independent R00 phase, she will then investigate changes in connectome architecture supporting the development of executive and emotional function using the ABCD longitudinal connectome and behavioral data (N=~11,000 age 9-14) (R00 Aim 3). During the K99 phase she will extend her training in behavioral neuroscience to include training in machine learning, longitudinal models, and computer science. Building on her strong foundation in human brain connectivity analysis, the applicant will gain advanced skills in biostatistics and best practices in software development to ensure her success as an independent researcher. The advisory committee, including Drs. Smyser (functional connectivity), Marcus (software engineering), Fair (developmental neuroscience), Todorov (biostatistics), Zhang (machine learning), Bassett (connectome analysis), Eggebrecht (toolbox development), and Barch (HCP/ABCD consultant) provide expertise in all core areas spanning experimental disciplines and possess an excellent record of obtaining independent funding and mentoring young scientists.